Burnishing wheel



Sept. 18, 1956 J. L. FEELEY BURNISHING WHEEL Filed March 4, 1955 A! li-nub Glass Fibers Bonded With Thermoset Resin INVENTOR John L. Feeley.

WITNESSES:

ATTORN Y United States BURNISHING WHEEL John L. Feeley, East McKeesport, Pa., assignor to Westinghonse Electric Corporation, East Pittsburgh, Pa, a corporation of Pennsylvania Application March 4, 1953, Serial No. 340,239

6 Claims. (Cl. 51-207) This invention relates to burnishing wheels particularly adapted for burnishing the edges of resinous members.

In the manufacture of many resinous products, there is a necessity for producing smooth polished edges in order to render the products commercially salable. In particular, laminates such, for example, as cotton fabric phenolics and melamine asbestos laminates are often sawed or punched, which operation produces a rough edge. In the present state of the art, the manufacturing schedule required for producing a smooth polished edge on each laminate requires at least two separate operations. Thus a punched cotton fabric phenolic laminate is first treated with an abrasive belt or wheel to remove irregular and excessive portions of the laminate to produce an even edge. The abrasive belt or wheel, however, leaves a rough surface and it requires a burnishing operation with, a set-up wheel to produce a reasonably smooth polished edge. The set-up wheel comprises a cotton buff to which alternate coats of cement and a fine abrasive have been applied. The operator performing the finishing operation with the set-up wheel must exercise considerable care and skill to prevent burning of the edges of the laminate as well as to produce a polished surface without gouging or adversely affecting the edge. The set-up wheel must be dressed frequently due to the loss of the abrasive coating thereon. Therefore, it would be apparent that it is an expensive operation to finish the edges of laminates under the present practice. Skilled operators are required to produce consistently good results. Furthermore, the output of finished product is relatively low. A considerable stock of set-up wheels and equipment for redressing such wheels is necessary.

The object of this invention is to provide a burnishing wheel that enables the complete burnishing of the edges of resinous members in one operation.

Another object of the invention is to provide a process for removing stock and polishing the edge of resinous members in a single operation.

Other objects of the invention will in part be obvious and will in part appear hereinafter. For a better understanding of the nature and objects of my invention, reference should be had to the following detailed description and drawing, in which the single figure is a perspective view of the burnishing wheel constructed in accordance with the invention.

I have discovered that a burnishing wheel comprising from 50% to 60% by weight of glass fibers and the balance being a thermoset resinous binder will enable the burnishing of the edges of all types ofresinous members in a single operation by rapidly and efliciently removing excess protuberances and irregular fragments to even up the edge and simultaneously polishing the edge of such members. It is necessary that the burnishing wheel operate at a speed such that its periphery is traveling at a velocity of at least 9,000 feet per minute. At slower speeds, the burnishing wheel does not function to entire satisfaction.

2,763,105 Patented Sept. 18, 1 956 At the present time, the accepted standard sets peripheral speeds of abrasive wheels and other polishing wheels as not to exceed 7,000 feet per minute. Therefore it will be seen that my burnishing wheel operates at peripheral speeds far above those used heretofore.

In producing a burnishing wheel in accordance with this invention, glass fiber fabric, such, for example, as woven glass cloth, is impregnated with a thermosettable resinous binder. A plurality of layers of the resin impregnated glass cloth are superimposed and molded in a press under heat and pressure to cure the resin to a thermoset state. The resulting laminate is then machined into a disc or body having a circular periphery and a central hole to enable it to be mounted on a shaft or arbor. The periphery of the resulting laminate will usually be provided with a plurality of burnishing grooves of a size and shape necessary to accommodate the particular resinous member to be burnished therewith. The disc is then mounted on a shaft and rotated at a speed to impart to the periphery of the wheel a surface velocity of from about 9,000 to 14,000 feet per minute. The edges of punched, sawed, or otherwise rough shaped laminates or other resinous members may be applied to the rotating wheel. It requires no great skill on the part of the operator to remove the uneven stock at the edge of the laminate whereby to produce an even edge and to cause it to be burnished to a smooth, nonporous edge.

Inasmuch as a high peripheral speed is required for successful burnishing, it is necessary that the wheel be prepared from a laminate in which the resin binder adheres strongly to the glass fibers. Particularly satisfactory resinous binders are melamine formaldehyde resins. A suitable melamine formaldehyde resin in one prepared by reacting 240 parts by weight of 37% formalin solution and 126 parts by weight of melamine. Two parts of a 10% solution of triethanolamine may be present. Reacting the mixture at C. for minutes will produce a partially reacted resinous syrup that may be diluted with ethanol. The resulting ethanol solution of the melamine formaldeyde reaction product may be applied to glass cloth. It will be necessary to dip the glass cloth in the melamine formaldeyde solution several times, drying the applied solution between passes in order to remove the solvent. Other melamine formaldehyde resins suitable for use in practicing the invention are disclosed in Patent 2,197,357.

The melamine formaldehyde resin impregnated glass cloth may be cut into circular or other shaped sheets and a sufficient number of plies superimposed to enable a Wheel or disc of the proper thickness to be produced therefrom. The superimposed layers of impregnated glass cloth are then molded at a temperature of C. to C. at a pressure of from 500 to 5,000 pounds per square inch.

Phenolic resins may be employed as the binders'for the glass fiber material. In order to secure the maximum strength, it may be desirable to precoat the glass fiber cloth with a small quanity of a mug oil modified phenolic resin as disclosed in Patent No. 2,372,048. The coating of glass cloth with the phenolic resin is carried out similarly to that previously described with respect to melamine resins.

Other thermosettable resins may be applied to glass cloth in proportions to produce a final product having from 50% to 60% by weight of the glass fibers. Suitable resins are polyester resins embodying an unsaturated resin and a liquid monomer having a reactive vinyl group. Examples of such are an alkyd resin comprising the reaction product of one mol of maleic anhydride, one mol of adipic acid and two mols of propylene glycol. This polyester is dissolved in monostyrene to provide 70 parts by weight of the alkyd resin and 30 parts by weight of monostyrene. Glass cloth may be treated with the polyester resin along with 0.5% by weight of a polymerization catalyst such as benzoyl peroxide and the whole cured to a thermoset state at a temperature of 150 C.

It may be desirable in some instances to add to the resinous binder a small amount of finely divided abrasive such as 200 mesh aluminum oxide. Up to of the weight of a melamine formaldehyde resin may comprise such finely divided abrasive material.

Referring to the figure of the drawing, there is illus trated a burnishing wheel 10 formed from a plurality of superimposed layers of woven glass and a thermoset melamine formaldehyde resin binder. A suitable wheel was one prepared from 45% by Weight of melamine resin, similar to the composition described above, and 55% by weight of glass cloth. The diameter of the wheel 10 was one foot. The wheel was provided with a central aperture not a diameter of one inch to enable it to be mounted on a one inch arbor. The speed of the arbor was 3,450 revolutions per minute. Therefore, the speed of the periphery 14 of the burnishing wheel was slightly more than 10,800 feet per minute. The periphery 14 of the Wheel was provided with a plurality of grooves 16. The sides of the groove were at an angle of 30 with respect to the diameter of the wheel. The bottoms of the grooves had a inch radius. The depth of the grooves was approximately inch. Laminated members of a thickness of A inch comprising cotton cloth and a phenolic resin having a rough edge resulting from a punching operation were burnished on the wheel 10 shown in the drawing. When applied against the rotating surface of the Wheel, the excess and protuberant material on the edges was rapidly removed by the action of the glass fibers in the burnishing wheel to produce an even edge and the edges were rapidly polished to a smooth surface. Dressing of the wheel to maintain the grooves in good shape was much less frequent than had been previously required with set-up wheels. The wheel 10 can be revolved in a lathe and the grooves 16 trued up with a tool.

The periphery 14 of the burnishing wheel 10 can be provided with a single channel of a shape corresponding to that desired at the finished edge.

It should be understood that the above drawing and description are examplary only of the above invention.

I claim as my invention:

1. A burnishing wheel comprising a rotatable body having a circular periphery, said body consisting essentially only of a plurality of superimposed laminations of glass fiber fabric and a thermoset resinous binder impregnating and bonding together the glass fibers in each fabric laminate and for binding the laminated fabric into a solid body capable of rotating at a speed such that the periphery of the body moves at a rate of from 9,000 to 14,000 feet per minute, the glass fibers comprising from 50% to of the weight of the body and the balance being the thermoset resinous binder, and said glass fibers being exposed at the periphery for burnishing contact with members applied thereagainst.

2. The burnishing wheel of claim 1, wherein the thermoset resinous binder is a melamine-aldehyde resin.

3. The burnishing wheel of claim 1, wherein the thermoset binder is a phenol aldehyde resin.

4. The burnishing wheel of claim 1, wherein the thermoset resinous binder includes up to 10% of its weight of a finely divided abrasive.

5. The burnishing wheel of claim 1, wherein the circular periphery includes a burnishing groove.

6. In the process of burnishing the surface of a resinous member, the steps comprising rotating a circular burnishing wheel consisting essentially of from 50% to 60% by weight of a plurality of superimposed layers of glass fiber fabric and from 50% to 40% by weight of a resinous binder, the glass fibers being exposed at the periphery of the wheel to a peripheral speed of at least 9,000 feet per minute and contacting the surface of the resinous member against the periphery of the rotating circular burnishing wheel whereby the surface of the resinous member is burnished rapidly and effectively by the cutting action of the exposed glass fibers.

References Cited in the file of this patent UNITED STATES PATENTS France Sept. 28, 

